Lignocellulosic biomass represents a vast resource for the production of renewable transportation fuels and chemicals to offset and replace current fossil fuel usage. For many decades, worldwide research efforts have focused on the development of cost-effective processes to selectively convert the polysaccharide components of plant cell walls, namely cellulose and hemicellulose, to fuels and chemicals through biological and chemical pathways. For example, in bioethanol production, biomass typically undergoes a mild thermochemical pretreatment step followed by enzymatic hydrolysis and fermentation to produce ethanol from the monomeric components of both cellulose and hemicellulose.
The lignin component of lignocellulosic biomass is an energy-dense, heterogeneous alkyl-aromatic polymer comprised of phenylpropanoid monomers used by plants for water transport and defense, and it is the second most abundant biopolymer on Earth after cellulose. Lignin is typically underutilized in most selective conversion processes for biofuel production. In the production of fuels and chemicals from biomass, lignin is typically burned for process heat because its inherent heterogeneity and recalcitrance make it difficult to selectively upgrade the monomers to value added products. This limited ability to utilize lignin, despite being the most energy dense polymer in the plant cell wall, is primarily due to its inherent heterogeneity and recalcitrance.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.